Trigger restarts on DAQ board

[mets501]

Hi.

I'm doing data acquisition with a DAQ board, the USB-6251 model.  I need something like the sample VI "Acq&Graph Voltage-Int Clk-HW Trig Restarts.vi", except I need the trigger to restart much more efficiently.  When I run that sample VI (and my own adaptation which is attached) I can only get trigger rates of about 30 Hz, and trigger that comes in within 30 ms of the previous one is just ignored.  I need it to handle trigger rates of up to 1 kHz. Does anyone have any ideas, or is there another way to go about it that will avoid this problem?

Thanks,

Jeremy

[rpursley8]

I think to get the response you want, you will have to use your Trigger signal to start generate the correct number of clock signals from a Counter.  See example 'Gen Dig Pulse Train-Finite-Retriggerable.vi'

Use Example 'Cont Acq&Graph Voltage-Ext Clk.vi' to actually do the acquisition.

For a test, set up as follows:

Set the Rate/Frequency to the same value.

Set the Number of Pulses/Samples to Read to the same value.

Set the Counter(s)/Clock Source to the same source

1. For the Gen Dig Pulse Train-Finite-Retriggerable.vi set Counter(s) to ctr0
2. For the Cont Acq&Graph Voltage-Ext Clk.vi set the Clock Source to Ctr0Out

Run the Cont Acq&Graph Voltage-Ext Clk.vi first and then quickly start the Gen Dig Pulse Train-Finite-Retriggerable.vi

You should see the acquired signal from whatever input you have connected.  I was able to do this without changing either example program.  Once you see it work, you can combine the two into one vi.
 

Message Edited by rpursley8 on 07-07-2009 04:19 PM

[rpursley8 · Accepted solution]

Attached is an example combining both together with an event structure to do the actual reading of the analog channel.

[mets501]

Wow, you're a lifesaver!  Thanks so much for your help, and for actually putting it together for me.

Jeremy

[Michael7331]

Is there any chance you could post a .jpg of the DAQmets program?  I'm running LabView 7.1, and can't see the contents of your program.

Thank you.

Michael

Message Edited by Michael7331 on 07-08-2009 11:49 AM

[mets501]

Yep, it's all attached.  Enjoy 🙂

[Michael7331]

Thank you very much for the quick and helpful reply!  Have a great day!

Michael

[Michael7331]

Thank you very much for the quick and helpful reply!  Have a great day!

Michael